Electric incandescent lamp



y 1962 H. CHAITEN 3,034,007

ELECTRIC INCANDESCENT LAMP Filed Jan. 23, 1959 I 1nvntof Herc Lol Chaiten,

b9 was/f His Atto neg.

United States 3,034,007 Patented May 8, 1962 ice My invention relatesgenerally to electric incandescent lamps and more particularly to lampsfor use in light projectors.

In certain applications, projection lamps having tubular gas-filledglass envelopes or bulbs are operated in a horizontal position.Projection lamps operate at considerably higher bulb and filamenttemperatures than ordinary incandescent lamps of comparable bulb size,and the hot convection currents arising from the filament impinge uponthe region of the bulb above the filament and sweep down around thesides of the bulb. In spite of the gas filling which, at least duringoperation of the lamp, is above atmospheric pressure and tends tominimize vaporizationof the filament, there is in fact considerablefilament evaporation which condenses to form a black deposit on thebulb. The black deposit causes increased absorption of heat by the bulbso that the bulb becomes plastic and is blistered or bulged outwardlyunder the pressure of the internal gas filling. This blackening anddeformation of the bulb renders the lamp useless well in advance of theend of the useful life of the filament and may seriously injure theprojector in which the lamp is used.

It has been proposed heretofore to employ anti-blackening grids orscreens arranged to be located above the filament during operation ofthe lamp whereby to intercept the material vaporized from the filamentand to break up the convection currents. In accordance with some ofthose proposals, the screen was in the form of an inverted V-shapedtrough arranged symmetrically above the filament. In at least someinstances, it has been found that even with a screen of relatively openstructure such an arrangement diverts sufficient of the convectioncurrents to the sides of the bulb to cause a gradual blistering orbulging of the bulb at those sides which spreads out toward the top toultimately merge and form one large blister or bulge. In certainprojection equipment, the lamp is located between a reflector and acondensing lens, and the bulging of that side of the bulb adjacent tothe lens (referred to hereinafter as the front of the bulb) isespecially critical because of the close spacing therebetween.

In accordance with the present invention, I have found that bulging ofthe front of the bulb can be substantially prevented by tilting theinverted V-shaped screen so that it is arranged asymmetrically with thatside or panel thereof nearer the front of the bulb inclined at an acuteangle below the horizontal and the other side or panel extendingsubstantially horizontally toward the rear of the bulb. Experience hasshown that not only is the blistering or bulging at the front and at thetop thereof substantially eliminated but, surprisingly, there is notendency to increase blistering at the rear of the bulb over the amountoccurring thereat with the screen symmetrically arranged with both sidesor panels obliquely oriented with respect to the vertical.

Further features and advantages of my invention will appear from thefollowing detailed description of a species thereof, and from thedrawing wherein:

FIG. 1 is a front elevation of a projection lamp embodying theinvention;

FIG. 2 is a cross-sectional view of the lamp taken along the line 2-2 ofFIG. 1, with a somewhat diagrammatic showing of an associated reflectorand condensing lens of a projector; and

FIG. 3 is a plan view of the screen before bending and with the positionof the'supporting member and the fila- 5 ment indicated thereon.

Referring to FIG. 1, the lamp comprises a tubular glass bulb 1containing a tungsten filament 2 herein illustrated as the biplane typecomprising a plurality of coiled wire sections arranged in staggeredrelation in closely parallel planes or, when desired, in a single plane.The filament 2 is arranged between support wires 3 and 4 substantiallyin a plane including the said wires 3, 4 and the axis of the bulb 1. Thefilament is electrically connected at its ends to wires 3 and 4 throughspuds 5. Wire 3 is supported from, and electrically connected to, alead-in or contact pin 6 and is also connected to a second pin 7 throughwire 8. Wire 4 is supported from and electrically connected to pin 9,and is also connected to a second pin 10 (FIG. 2) through a conductor 11which bridges pins 9 and'10 and which may be a fuse wire.

The filament 2 is supported at each end by a plurality of support wires12 whichenage the bight portions connecting successive coil segments ofthe filament and are supported from glass bridges 13 which are, in turn,supported from the support wires 3 and 4. The bulb 1 contains a fillingof inert gas, preferably nitrogen, at a substantial pressure, preferablyabout600 mm. of mercury, or higher, at room temperature.

In accordance with the invention, the lamp contains a screen 14 mountedalong its longitudinal center line on the upper support wire Bto beabove the filament .2 in normal use of the lamp. As shown in FIG. 2, thelamp isemployed. in a projector in association with a sphericalreflector 15 at the rear of the lamp and a condensing lens 16 at thefront of the lamp. The screen 14 is folded along its longitudinal centerline to form two sides or panels 117 and 18; the panel 17 extendsrearwardly in a plane substantially normal to the vertical planeincluding the wires 3, 4 and the bulb axis so as to be in a horizontalposition in use of the lamp, whereas the panel 18 extends toward thefront of the lamp in a plane inclined at an angle of about 45 below thehorizontal. Although the form of the screen 14 maybe variedconsiderably, it is shown herein in connection with a 500 watt lamphaving a bulb 1 of soft lime glass having a softening point of about 690C., a diameter of 1% inches and a length of about 3% inches, and whereinthe screen is formed from sheet nickel about .015 inch thick, inch longand inch wide. The screen is formed with a row of four holes 19 alongeach longitudinal edge, and a central row of holes 20; the holes 19 areabout 7 inch by inch, and the central holes 20 are each about inch byinch. In this case, the area of the openings 19 and 20 constitutes about60% of the total area of the screen 14. I have also found that bestresults are obtained when the screen 14 is not centered longitudinallyover the filament but is displaced toward the base of the lamp with thecenter line 21 (FIG. 3) of a transverse series of holes 19, 20, -'19over the center of the filament 2.

With the lamp mounted in a projector as shown in FIG. 2, a portion ofthe convection currents rising along the right hand side of the filament2 strikes the tilted side or panel 18 of the screen :14 and aredeflected away from the front of the bulb Ladjacent the lens 1 6 withthe result that blistering thereof is eliminated; at the same time,perhaps because those currents are somewhat cooled in their travelacross panels 18 and 17 toward the back of the bulb, they do not causeany increased tendency to blistering at the back of the bulb. Tests haveshown a still lesser tendency to blistering when the screen -1 4 isofiset longitudinally toward the base of the lamp, as shown in FIG. 1and as indicated in FIG. 3, so that the transverse centerline 21 of thefilament 2 is at the center of a transverse series of holes 19, 29,19;

. In spite of the relatively open structure of the screen 14,

it also intercepts particles of tungsten vaporized from the filament 2,to maintain the bulb walls essentially free.

from blackening. I

What I claimas new and desire to secure by Letters Patent of the UnitedStates is:

1. An electric incandescent lamp comprising a tubular gas-filled glassbulb, support members extending longitudinall'y within said bulb, afilament mounted between said members substantially in a plane includingsaid members and the axis of said bulb, and a heat shielding anddeflecting screen member having a-plurality of openings and-extendinglongitudinally in said bulb at the side of the filament to pass throughsaid openings, and presenting adeflecting obstruction to another portionof said curand extending longitudinally in said bulb above said filamentand attached along its longitudinal center line to the said uppersupport member, said screen being bent along its said center line toform two panels, one of said panels being in a substantially horizontalplane and the other panel being in a plane tilted downward at an acuteangle to the horizontal, said screen allowing a portion of theconvection currents arising from the filament to pass through saidopenings and presenting a deflecting obstruction to another portion ofsaid currents.

3. An electric incandescent lamp comprising a tubular gas-filled glassbulb, support members extending longitudinally within said bulb, afilament mounted between said members substantially in a plane includingsaid memrents when the lamp is operated horizontally with thefirst-mentioned plane vertical and the screen above the filament.

2..In a projector", an incandescent lamp having a horizontally disposedtubular gas-filled bulb, an upper and a lower support member extendinglongitudinally and horizontally within said bulb, a filament mountedsubstantially in a vertical plane including said support members and theaxis of said bulb, and a heat shielding and deflecting screen memberhaving'a plurality of openings bers and the axis of said bulb, and aheat shielding and deflecting screen member having a plurality oflongitudinal and transverse rows of openings and extendinglongitudinally in said bulb at the side of said filament with itslongitudinal center line in said plane and with a transverse row of saidopenings centered over the center of said filament, said screenbeingbent along its said longitudinal center line to form two panels,one of said panels being in a second plane substantially normal to thefirstmentioned plane including the bulb axis and the other I panel beingin a third plane tilted toward the filament at an acute angle to thesaid first-mentioned plane, said screen allowing a portion of theconvection currents arising from the filament to pass through saidopenings and presentingv a deflecting obstruction to another portion ofsaid currents when the lamp is operated horizontally with thefirst-mentioned plane vertical and the screen above the filament.

References Cited in the file of this patent UNITED STATES PATENTS1,967,906 Ruttenauer July 24, 1934 2,326,419 Van Horn Aug. 10, 19432,862,125 Biggs- Nov. 25, 195.8

